package org.json;

/*
Copyright (c) 2002 JSON.org

Permission is hereby granted, free of charge, to any person obtaining a copy 
of this software and associated documentation files (the "Software"), to deal 
in the Software without restriction, including without limitation the rights 
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 
copies of the Software, and to permit persons to whom the Software is 
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all 
copies or substantial portions of the Software.

The Software shall be used for Good, not Evil.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 
SOFTWARE.
*/

import java.text.ParseException;

/**
 * A JSONTokener takes a source string and extracts characters and tokens from
 * it. It is used by the JSONObject and JSONArray constructors to parse
 * JSON source strings.
 * @author JSON.org
 * @version 0.1
 */
public class JSONTokener {

    /**
     * The index of the next character.
     */
    private int myIndex;


    /**
     * The source string being tokenized.
     */
    private String mySource;


    /**
     * Construct a JSONTokener from a string.
     *
     * @param s     A source string.
     */
    public JSONTokener(String s) {
        myIndex = 0;
        mySource = s;
    }


    /**
     * Back up one character. This provides a sort of lookahead capability,
     * so that you can test for a digit or letter before attempting to parse
     * the next number or identifier.
     */
    public void back() {
        if (myIndex > 0) {
            myIndex -= 1;
        }
    }



    /**
     * Get the hex value of a character (base16).
     * @param c A character between '0' and '9' or between 'A' and 'F' or
     * between 'a' and 'f'.
     * @return  An int between 0 and 15, or -1 if c was not a hex digit.
     */
    public static int dehexchar(char c) {
        if (c >= '0' && c <= '9') {
            return c - '0';
        }
        if (c >= 'A' && c <= 'F') {
            return c + 10 - 'A';
        }
        if (c >= 'a' && c <= 'f') {
            return c + 10 - 'a';
        }
        return -1;
    }


    /**
     * Determine if the source string still contains characters that next()
     * can consume.
     * @return true if not yet at the end of the source.
     */
    public boolean more() {
        return myIndex < mySource.length();
    }


    /**
     * Get the next character in the source string.
     *
     * @return The next character, or 0 if past the end of the source string.
     */
    public char next() {
        char c = more() ? mySource.charAt(myIndex) : 0;
        myIndex += 1;
        return c;
    }


    /**
     * Consume the next character, and check that it matches a specified
     * character.
     * @throws ParseException if the character does not match.
     * @param c The character to match.
     * @return The character.
     */
    public char next(char c) throws ParseException {
        char n = next();
        if (n != c) {
            throw syntaxError("Expected '" + c + "' and instead saw '" +
                    n + "'.");
        }
        return n;
    }


    /**
     * Get the next n characters.
     * @exception ParseException
     *   Substring bounds error if there are not
     *   n characters remaining in the source string.
     *
     * @param n     The number of characters to take.
     * @return      A string of n characters.
     */
     public String next(int n) throws ParseException {
         int i = myIndex;
         int j = i + n;
         if (j >= mySource.length()) {
            throw syntaxError("Substring bounds error");
         }
         myIndex += n;
         return mySource.substring(i, j);
     }


    /**
     * Get the next char in the string, skipping whitespace
     * and comments (slashslash and slashstar).
     * @throws ParseException
     * @return  A character, or 0 if there are no more characters.
     */
    public char nextClean() throws java.text.ParseException {
        while (true) {
            char c = next();
            if (c == '/') {
                switch (next()) {
                case '/':
                    do {
                        c = next();
                    } while (c != '\n' && c != '\r' && c != 0);
                    break;
                case '*':
                    while (true) {
                        c = next();
                        if (c == 0) {
                            throw syntaxError("Unclosed comment.");
                        }
                        if (c == '*') {
                            if (next() == '/') {
                                break;
                            }
                            back();
                        }
                    }
                    break;
                default:
                    back();
                    return '/';
                }
            } else if (c == 0 || c > ' ') {
                return c;
            }
        }
    }


    /**
     * Return the characters up to the next close quote character.
     * Backslash processing is done. The formal JSON format does not
     * allow strings in single quotes, but an implementation is allowed to
     * accept them.
     * @exception ParseException Unterminated string.
     * @param quote The quoting character, either <code>"</code>&nbsp;<small>(double quote)</small> or <code>'</code>&nbsp;<small>(single quote)</small>.
     * @return      A String.
     */
    public String nextString(char quote) throws ParseException {
        char c;
        StringBuffer sb = new StringBuffer();
        while (true) {
            c = next();
            switch (c) {
            case 0:
            case 0x0A:
            case 0x0D:
                throw syntaxError("Unterminated string");
            case '\\':
                c = next();
                switch (c) {
                case 'b':
                    sb.append('\b');
                    break;
                case 't':
                    sb.append('\t');
                    break;
                case 'n':
                    sb.append('\n');
                    break;
                case 'f':
                    sb.append('\f');
                    break;
                case 'r':
                    sb.append('\r');
                    break;
                case 'u':
                    sb.append((char)Integer.parseInt(next(4), 16));
                    break;
                case 'x' :
                    sb.append((char) Integer.parseInt(next(2), 16));
                    break;
                default:
                    sb.append(c);
                }
                break;
            default:
                if (c == quote) {
                    return sb.toString();
                }
                sb.append(c);
            }
        }
    }


    /**
     * Get the text up but not including the specified character or the
     * end of line, whichever comes first.
     * @param  d A delimiter character.
     * @return   A string.
     */
    public String nextTo(char d) {
        StringBuffer sb = new StringBuffer();
        while (true) {
            char c = next();
            if (c == d || c == 0 || c == '\n' || c == '\r') {
                if (c != 0) {
                    back();
                }
                return sb.toString().trim();
            }
            sb.append(c);
        }
    }


    /**
     * Get the text up but not including one of the specified delimeter
     * characters or the end of line, which ever comes first.
     * @param delimiters A set of delimiter characters.
     * @return A string, trimmed.
     */
    public String nextTo(String delimiters) {
        char c;
        StringBuffer sb = new StringBuffer();
        while (true) {
            c = next();
            if (delimiters.indexOf(c) >= 0 || c == 0 ||
                    c == '\n' || c == '\r') {
                if (c != 0) {
                    back();
                }
                return sb.toString().trim();
            }
            sb.append(c);
        }
    }


    /**
     * Get the next value. The value can be a Boolean, Double, Integer,
     * JSONArray, JSONObject, or String, or the JSONObject.NULL object.
     * @exception ParseException The source conform to JSON syntax.
     *
     * @return An object.
     */
    public Object nextValue() throws ParseException {
        char c = nextClean();
        String s;

        if (c == '"' || c == '\'') {
            return nextString(c);
        }
        if (c == '{') {
            back();
            return new JSONObject(this);
        }
        if (c == '[') {
            back();
            return new JSONArray(this);
        }
        StringBuffer sb = new StringBuffer();
        char b = c;
        while (c >= ' ' && c != ':' && c != ',' && c != ']' && c != '}' &&
                c != '/') {
            sb.append(c);
            c = next();
        }
        back();
        s = sb.toString().trim();
        if (s.equals("true")) {
            return Boolean.TRUE;
        }
        if (s.equals("false")) {
            return Boolean.FALSE;
        }
        if (s.equals("null")) {
            return JSONObject.NULL;
        }
        if ((b >= '0' && b <= '9') || b == '.' || b == '-' || b == '+') {
            try {
                return new Integer(s);
            } catch (Exception e) {
            }
            try {
                return new Double(s);
            } catch (Exception e) {
            }
        }
        if (s.equals("")) {
            throw syntaxError("Missing value.");
        }
        return s;
    }


    /**
     * Skip characters until the next character is the requested character.
     * If the requested character is not found, no characters are skipped.
     * @param to A character to skip to.
     * @return The requested character, or zero if the requested character
     * is not found.
     */
    public char skipTo(char to) {
        char c;
        int index = myIndex;
        do {
            c = next();
            if (c == 0) {
                myIndex = index;
                return c;
            }
        } while (c != to);
        back();
        return c;
    }


    /**
     * Skip characters until past the requested string.
     * If it is not found, we are left at the end of the source.
     * @param to A string to skip past.
     */
    public void skipPast(String to) {
        myIndex = mySource.indexOf(to, myIndex);
        if (myIndex < 0) {
            myIndex = mySource.length();
        } else {
            myIndex += to.length();
        }
    }


    /**
     * Make a ParseException to signal a syntax error.
     *
     * @param message The error message.
     * @return  A ParseException object, suitable for throwing
     */
    public ParseException syntaxError(String message) {
        return new ParseException(message + toString(), myIndex);
    }


    /**
     * Make a printable string of this JSONTokener.
     *
     * @return " at character [myIndex] of [mySource]"
     */
    public String toString() {
        return " at character " + myIndex + " of " + mySource;
    }


    /**
     * Unescape the source text. Convert <code>%</code><i>hh</i> sequences to single characters,
     * and convert plus to space. There are Web transport systems that insist on
     * doing unnecessary URL encoding. This provides a way to undo it.
     */
    void unescape() {
        mySource = unescape(mySource);
    }

    /**
     * Convert <code>%</code><i>hh</i> sequences to single characters, and convert plus to space.
     * @param s A string that may contain <code>+</code>&nbsp;<small>(plus)</small> and <code>%</code><i>hh</i> sequences.
     * @return The unescaped string.
     */
    public static String unescape(String s) {
        int len = s.length();
        StringBuffer b = new StringBuffer();
        for (int i = 0; i < len; ++i) {
            char c = s.charAt(i);
            if (c == '+') {
                c = ' ';
            } else if (c == '%' && i + 2 < len) {
                int d = dehexchar(s.charAt(i + 1));
                int e = dehexchar(s.charAt(i + 2));
                if (d >= 0 && e >= 0) {
                    c = (char)(d * 16 + e);
                    i += 2;
                }
            }
            b.append(c);
        }
        return b.toString();
    }
}